Other blue creatures you control will get +1/+1 whether they are artifacts or not.

1/1/2011

Turning an artifact creature blue with the second ability will override any other color(s) the creature previously had. It will still be an artifact. You may target a blue artifact creature with this ability.

1/1/2011

Since Grand Architect’s last ability doesn’t have a tap symbol in its cost, you can tap a blue creature (including Grand Architect itself) that hasn’t been under your control since your most recent turn began to pay the cost.